JP2003094363A - Attitude determining method and device for articulated robot - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize a robot attitude at each working step and shorten a cycle time. SOLUTION: The robot attitude is calculated at each working step in a work forward direction (step S5). A robot attitude with the shortest transit time and the minimum tool attitude deviation is selected (step S7 and S10). A robot attitude at a terminal working step in a work reverse direction is calculated (step S15). The robot attitude is corrected by comparing it with a robot attitude at a terminal working step determined in the work forward direction (step S20). Correction of the robot attitude is carried out as far as a group where a transit time between groups of working steps sorted by similar relationships is maximum (step S26).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to each of the working points when the articulated robot is moved to a plurality of working points from an original position set in an initial posture and then returned to the original position in the initial posture. And a method for determining a robot posture in the same.

[0002]

2. Description of the Related Art Conventionally, when an articulated robot installed on a manufacturing line is directly operated to teach a work posture, an operator who is familiar with the operation of the articulated robot must perform the work on the site of the manufacturing line. Therefore, the work becomes inefficient accordingly. Further, since such work needs to be performed while the manufacturing line is stopped, the operating rate of the manufacturing line also decreases.

Therefore, in recent years, in order to improve the efficiency of the teaching work or to improve the operating rate of the manufacturing line, teaching is performed offline. That is, a model of an articulated robot and a work or a peripheral structure which is a work object is built on a computer, teaching data is created using this model, and the teaching data is supplied to the articulated robot in the field. This makes it possible to efficiently create teaching data without stopping the production line.

By the way, in the production line, it is required to improve the productivity, and in order to meet the demand, it is necessary to study the reduction of the cycle time by the articulated robot.

However, in the conventional teaching, data is basically created so that the end effector of the articulated robot can be set at a predetermined work point in a predetermined posture, and the postures of the joints of the articulated robot ( In the following, it was not considered enough to say "robot posture").

For example, as shown in FIG. 7, the positions of the joints 4a to 4e of the articulated robot 2 may be in various states even if the position and orientation of the end effector 6 with respect to the work point 8 are the same. Can be taken. Further, as shown in FIG. 8, when the end effector 6 is moved from the work point 8a to the adjacent work point 8b, the work points 8a and 8b are moved.
Even if the posture of the end effector 6 is the same,
As can be seen from the states of (a) and (b), the axis of the end effector 6 may be inverted and set.

As described above, if only the position and posture of the end effector at the working point are considered and the posture and state of each joint are not considered, the cycle time cannot be shortened sufficiently. .

On the other hand, a recent production line has a large number of articulated robots arranged in a narrow area, so that each articulated robot can perform its work without interfering with each other. In some cases, the initial posture of each articulated robot must be set while being considerably restricted. After moving each articulated robot in such a state from the original position to each work point, when trying to return to the original position with the same initial posture, especially when the robot posture and the original position at the final work point are changed. It is feared that the robot posture will greatly differ from that of the robot posture and the movement time between them will affect the cycle time.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and provides a multi-joint robot capable of optimizing the robot posture at each work point and shortening the cycle time. An object is to provide a posture determining method and device.

[0010]

In order to solve the above-mentioned problems, in the method of the present invention, the articulated robot is moved to a plurality of work points from the original position set to the initial posture, and then the original position is set to the original position. A method of determining a robot posture at each of the work points when returning in the initial posture, wherein when moving the articulated robot in a work forward direction from the original position,
A step of obtaining a robot posture that can move with respect to each work point in the shortest movement time for each work point, and according to the robot posture at each work point, divides each work point into a plurality of groups in the work forward direction. A step of classifying, a step of obtaining the group on the downstream side in the work forward direction that maximizes the shortest movement time between the groups, and a case of moving the articulated robot in the work reverse direction from the original position. A step of obtaining a robot posture that can move with respect to each work point in the shortest movement time up to the work points forming the downstream group, and a robot posture at each work point obtained in the work forward direction To
A step of correcting the robot posture at each of the work points obtained in the reverse direction of the work.

In this case, the robot posture is calculated in the reverse work direction up to the group of work points where the movement time of the articulated robot is maximum, and the robot posture at each work point obtained in the forward work direction is corrected by the robot posture. To do. With this modification, the difference between the initial posture at the original position and the robot posture at the final work point is absorbed by the corrected robot posture, so the movement time between the original position and the final work point can be shortened. As a result, the cycle time of the articulated robot can be shortened.

Further, in the apparatus of the present invention, after moving the articulated robot from the original position set to the initial posture to a plurality of work points, the work points at each of the work points when returning to the original position in the initial posture are described. A device for determining a robot posture,
A robot posture calculation unit that calculates the robot posture at each work point, a robot movement time calculation unit that calculates the movement time between each work point and each work point from the original position, and for each work point According to the robot posture selection unit that selects the robot posture that minimizes the movement time for each work point, and the robot posture at each work point, the work points are classified into a plurality of groups in the work forward direction, and A group selection unit that selects the downstream group in the work forward direction that maximizes the movement time between the groups, and the downstream group that is obtained by moving the articulated robot in the work forward direction. The robot posture of the working point constituting the robot is corrected by the robot posture obtained by moving the articulated robot in the reverse working direction from the original position. Characterized in that it comprises a robot posture correcting portion.

[0013]

1 is a block diagram of an off-line teaching apparatus 10 according to an embodiment to which a posture determining method and apparatus of an articulated robot according to the present invention are applied, and teaching data created by the off-line teaching apparatus 10 is applied. 1 shows a schematic configuration of the articulated robot 12 that is to be used.

The articulated robot 12 is equipped with an end effector 22 such as a welding gun which is connected to the base 14 via a plurality of rotatable links 16, 18 and 20, and is set in a robot controller 24. Operates according to teaching data. The articulated robot 12 and the robot control unit 24 are arranged on the production line at the site.

The off-line teaching device 10 is composed of a computer, and as shown in FIG.
CPU 28 for controlling the entire system and ROM as a storage unit
30 and RAM 32, and hard disk drive 34
Hard disk 36 where data is read and written by
A recording medium drive 40 for reading and writing teaching data and the like from an external recording medium 38 such as a flexible disk or a compact disk, and the articulated robot 12
The teaching data creation circuit 42 for creating the teaching data and the simulation circuit 44 for performing the operation simulation of the articulated robot 12 based on the created teaching data. The control unit 26
Is a display 4 for assisting the teaching work by an operator and displaying a simulation image.
6 is connected via a drawing control circuit 48, and a keyboard 52 and a mouse 54 are connected via an interface 50.

On the hard disk 36, a teaching data creation program 56 for creating teaching data of the articulated robot 12, the articulated robot 12,
Shape data 58 related to the work object and other equipment
And robot specification data 60 including operation specifications of each axis of the articulated robot 12 are stored.

The teaching data creation circuit 42 is shown in FIG.
3, the shape data 58, the robot specification data 60, the work point data set by the operator, and the articulated robot 1 stored in the hard disk 36.
The robot posture calculation unit 6 that calculates the robot posture of the articulated robot 12 based on the initial posture data at the original position of 2.
2, the robot movement time calculation unit 64 that calculates the movement time of the articulated robot 12 from the original position to the work point and each work point based on the shape data 58 and the robot specification data 60; It basically comprises a robot posture calculation circuit 66 for calculating the robot posture and a robot posture correction circuit 68 for correcting the robot posture at each work point.

The robot posture calculation circuit 66 has a minimum tool posture deviation calculation unit 70, a shortest movement time calculation unit 72, and a robot posture selection unit 74.

The minimum tool posture deviation calculation unit 70 calculates the smallest posture deviation (posture change amount) among the posture deviations of the end effector 22 reaching the plurality of robot postures at each work point for each work point. The shortest movement time calculation unit 72 calculates, for each work point, the shortest movement time among the movement times for reaching the plurality of robot postures at each work point. Robot posture selection unit 7
4 is whether the moving time of the articulated robot 12 is the shortest,
Alternatively, the robot posture that minimizes the posture deviation of the end effector 22 is selected for each work point.

The robot posture correction circuit 68 has a robot posture comparison unit 76, a group setting unit 78, a maximum inter-group movement time calculation unit 80, an inter-group movement time comparison unit 82, and a robot posture correction unit 84. The group setting unit 78, the maximum inter-group travel time calculation unit 80, and the inter-group travel time comparison unit 82 form a group selection unit.

The robot posture comparing unit 76 detects the robot posture of the articulated robot 12 at each work point obtained in the work forward direction by the robot posture calculation circuit 66 and the articulated robot 12 at each work point obtained in the opposite work direction. Compare with robot pose. The group setting unit 78 classifies each work point into a plurality of groups in the work forward direction according to the robot posture of the articulated robot 12 moving between the plurality of work points. Specifically, for example, the postures of the end effector 22 of the articulated robot 12 that change little and the movement time difference is not large can be set as a group.
The maximum inter-group movement time calculation unit 80 calculates the maximum movement time among the movement times of the articulated robot 12 between the groups set by the group setting unit 78. The inter-group moving time comparing unit 82 compares the maximum inter-group moving time calculated by the maximum inter-group moving time calculating unit 80 with the inter-group moving time in the work forward direction for the group including the work point for correcting the robot posture. To do. The robot posture correction unit 84 gives an instruction to correct the robot posture for the work point based on the comparison result by the robot posture comparison unit 76 and the inter-group movement time comparison unit 82.

The offline teaching apparatus 10 of this embodiment is basically constructed as described above, and its operation will be described below with reference to the flow charts shown in FIGS. 4 and 5 and the explanatory view of FIG. To do.

Prior to the teaching data creation, the teaching data creation program 56 is read from the hard disk 36 and loaded into the teaching data creation circuit 42. Next, the hard disk 36 stores the shape data 58 relating to the articulated robot 12, the work object and other equipment, and the robot specification data 60 such as the maximum speed, the maximum acceleration, and the movable range of each axis of the articulated robot 12. Is read (step S1).

Next, the operator sets the robot posture of the articulated robot 12 which is the initial posture when the end effector 22 is placed at the original position D0 (step S).
2, see FIG. 6). This initial posture is set in consideration of the arrangement of other articulated robots 12 arranged in the vicinity.

Further, the operator is the end effector 2
The positions of the work points D1, D2, ... Of No. 2 and the tool posture (the posture of the end effector 22) are set (step S3). Note that the tool posture is usually set so that the end effector 22 is flush with the surface of the object to be welded when the articulated robot 12 is a welding robot. Therefore, the tool posture can be automatically set based on the shape data 58.

After the above preparatory steps are completed, the calculation of the robot posture at each work point D1, D2, ... The "forward direction" means that, in FIG. 6, the articulated robot 12 starts from the original position D0 and moves in the order of work points D1, D2, ..., Dm (m: work point number) ,. , The work direction of returning to the original position D0.

First, the robot posture calculation unit 62 sets the work point number m = 1 (step S4), and the end effector 2
The robot posture at the work point D1 when moving 2 from the original position D0 to the work point D1 is calculated (step S5).
In this case, as described in FIG. 7, a plurality of robot postures at the work point D1 may be obtained.

Therefore, the robot movement time calculation unit 64 is
For the plurality of robot postures obtained in step S5,
The time required to move the articulated robot 12 from the original position D0 to the work point D1 is calculated (step S).
6). Next, the shortest movement time calculation unit 72 obtains the shortest movement time from the calculated movement times for each robot posture. The robot posture selection unit 74 selects the robot posture having the shortest movement time calculated by the shortest movement time calculation unit 72 as the robot posture at the work point D1 (step S7).

On the other hand, the same for a plurality of robot postures,
Alternatively, when the substantially same shortest movement time is obtained (step S8), the robot posture calculation unit 62 calculates the posture deviation of the end effector 22 in a plurality of robot postures that can be regarded as the shortest movement time (step S9).
Next, the minimum tool posture deviation calculation unit 70 obtains the minimum posture deviation from the calculated posture deviations. The robot posture selection unit 74 selects a robot posture in which the end effector 22 has the smallest posture deviation from a plurality of robot postures that can be regarded as having the same shortest movement time (step S10).

Final work point D with work point number m = m + 1
The robot posture is similarly obtained up to M (M: number of work points) (steps S11 and S12).

Next, the group setting section 78 determines each work point D.
1 to DM are classified into groups G1 to GN (N: number of groups) (step S13). In addition, groups G1 to GN
As the classification criteria of, for example, when performing a welding operation, those having similar working conditions such as a working point where the attitude of the end effector 22 with respect to the welded object is small and a working position being close It can be set to be grouped. In this case, the operator may group the work points D1 to DM in advance.

When the number N of groups is 1 (step S1)
4), the robot posture is calculated in the forward direction in step S1.
Determine the final robot posture from the ones obtained up to 2.
The process ends.

When the number N of groups is 2 or more, that is,
When the work points D1 to DM are classified into a plurality of groups, calculation of the robot posture at each final work point DM to D1 in the backward calculation is started. The “reverse direction” means that in FIG.
, The articulated robot 12 starts in the opposite direction from the original position D0, and the working points D9, D8, ..., Dm ,.
The work direction is to return to the original position D0 after moving in the order of.

First, the robot posture calculation unit 62 calculates the robot posture at the final work point DM when the end effector 22 is moved from the original position D0 to the final work point DM (step S15). Next, the robot movement time calculation unit 64 calculates the time required to move the articulated robot 12 from the original position D0 to the final work point DM for each of the plurality of robot postures obtained in step S15 (step S16). The robot posture selection unit 74
Similar to the process in the forward calculation in steps S7 to S10, the robot posture that can be regarded as the shortest movement time and has the minimum posture deviation of the end effector 22 is selected (step S17).

Next, the robot posture comparing section 76 compares the robot posture of the final work point DM obtained in the forward work direction of step S10 with the robot posture of the final work point DM obtained in the reverse work direction of step S17. Yes (step S1
8).

The robot posture correcting unit 84 determines whether or not the robot posture of the final work point DM needs to be corrected based on the comparison result by the robot posture comparing unit 76 (step S19). When it is determined that the difference between the robot postures is within the allowable range, the robot postures of the respective work points D1 to DM obtained by the forward calculation are determined as the final robot postures, and the processing ends.

On the other hand, when it is determined that the robot posture needs to be corrected, the robot posture at the final work point DM is corrected to the robot posture obtained by the backward calculation, and the robot posture calculation unit 62 Instructing the calculation and correction of the robot posture by the backward calculation for each work point (work points D9 to D7 in FIG. 6) in the group GN (step S20).

After obtaining the robot posture by backward calculation up to the first working point of the final group GN, the robot posture comparing unit 76 determines the first working point (working point D in the case of FIG. 6).
The robot posture calculated by the backward calculation in 7) is compared with the robot posture calculated by the forward calculation of the same work point (step S21).

The robot posture correction section 84 executes step S2.
From the comparison result by the robot posture comparing unit 76 in No. 1, it is determined whether or not to continue the robot posture correction process for the work points in the group G (N-1) (step S22). When it is determined that the difference between the robot postures is within the allowable range, the robot postures of the respective work points in the groups G1 to G (N-1) obtained by the forward calculation and the group GN obtained by the backward calculation. The robot posture of each work point inside is determined as the final robot posture, and the processing is ended.

On the other hand, when it is determined that the correction of the robot posture needs to be continued, the maximum inter-group movement time calculation unit 8
0 is an articulated robot 12 between the groups G1 to GN.
The moving time of is calculated (step S23). This movement time is, for example, as shown in FIG. 6, the movement time T12 between the last work point D3 of the group G1 and the first work point D4 of the group G2, the last work point D6 of the group G2 and the first work point D3 of the group G3. Can be obtained as the moving time T23 between the work points D7.

Next, the maximum inter-group movement time calculation unit 80
Determines the maximum travel time (maximum inter-group travel time) from the travel times between the groups G1 to GN obtained in step S23 (step S24).

Therefore, after setting the group number n to the number of groups N (step S25), the inter-group moving time comparing unit 82 compares the maximum inter-group moving time obtained in step S24 with the group G (N-1) and The moving time between groups GN (moving time between groups T (N-1), N) is compared (step S26), and moving time T between groups is compared.
(N-1), where N is the maximum inter-group travel time,
It is determined that the change in the robot posture can be sufficiently absorbed between the group G (N-1) and the group GN, and the processing is ended.

On the other hand, the intergroup moving time T (N-1),
When N is not the maximum inter-group movement time, n = n-1 is set (step S27), and the robot posture with respect to the work point in the group Gn is corrected (steps S28 and S29), as in steps S20 to S22. . The robot posture correction process is performed by moving time between groups T (n-
1), group Gn where n is the maximum inter-group travel time
Is done until.

The robot posture at each work point obtained as described above is set in the hard disk 36 as a part of the teaching data, then the operation is confirmed by the simulation circuit 44, and the external operation is performed via the recording medium drive 40. It is recorded on the recording medium 38. Next, the teaching data recorded in the external recording medium 38 is downloaded to the robot controller 24 and used for controlling the articulated robot 12.

[0045]

As described above, according to the present invention, when the articulated robot is moved from the original position set in the initial posture to each work point and then returned to the original position in the same posture, the original position is restored. It is possible to set a robot posture capable of moving the articulated robot in the shortest movement time between and between the work points and between the work points.

As a result, the cycle time of work by the articulated robot can be shortened and productivity can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an offline teaching device and an articulated robot of this embodiment.

FIG. 2 is a circuit configuration diagram of an offline teaching device of the present embodiment.

FIG. 3 is a block diagram of a teaching data creation circuit in the offline teaching device of the present embodiment.

FIG. 4 is a flowchart of a posture determining method of an articulated robot in the offline teaching device of the present embodiment.

FIG. 5 is a flowchart of a posture determining method of an articulated robot in the offline teaching device of the present embodiment.

FIG. 6 is an explanatory diagram of a posture determining method of an articulated robot in the offline teaching device of the present embodiment.

FIG. 7 is an explanatory diagram of a plurality of robot postures with respect to the same work point in an articulated robot.

FIG. 8 is an explanatory diagram of different tool postures in the articulated robot.

[Explanation of symbols]

10 ... Offline teaching device 12 ... Articulated robot 24 ... Robot control unit 26 ... Control unit 36 ... Hard disk 42 ... Teaching data creation circuit 44 ... Simulation circuit 56 ... Teaching data creation program 58 ... Geometry data 60 ... Robot specification data 62 ... Robot Posture calculation unit 64 ... Robot movement time calculation unit 66 ... Robot posture calculation circuit 68 ... Robot posture correction circuit 70 ... Minimum tool posture deviation calculation unit 72 ... Shortest movement time calculation unit 74 ... Robot posture selection unit 76 ... Robot posture comparison unit 78 ... Group setting unit 80 ... Maximum inter-group movement time calculation unit 82 ... Inter-group movement time comparison unit 84 ... Robot posture correction unit

Continued front page    (72) Inventor Kaoru Shibata             1-10-1 Shinsayama, Sayama City, Saitama Prefecture             Engineering Co., Ltd. F term (reference) 3C007 AS11 BS12 BT08 CT05 CV08                       CW08 LS10 LS15 LS20 MT01                 5H269 AB12 AB33 BB09 CC09 DD06                       QC10 SA10 SA11

Claims (5)

[Claims] 1. A method for determining a robot posture at each work point when the articulated robot is moved to a plurality of work points from an original position set in the initial posture and then returned to the original position in the initial posture. And when moving the articulated robot from the original position in the work forward direction, obtaining a robot posture that can be moved in the shortest movement time for each work point for each work point, Classifying each of the work points into a plurality of groups in the work forward direction according to the robot posture at the work point; and the group on the downstream side in the work forward direction in which the shortest movement time between the groups is maximum. And a robot posture that is movable in the shortest movement time with respect to each of the work points when the articulated robot is moved in the work reverse direction from the original position, A step of obtaining the work points forming the group on the downstream side; and a robot posture at each work point obtained in the work forward direction is corrected by a robot posture at each work point obtained in the work reverse direction. A method for determining a posture of an articulated robot, comprising: 2. The method according to claim 1, wherein when there are a plurality of robot postures in which the shortest movement time when moving the multi-joint robot from the original position to each of the work points is substantially the same, A posture determining method for an articulated robot, characterized in that a posture of a robot having a minimum posture deviation of an end effector of the robot is selected. 3. The method according to claim 1, wherein the robot posture of the work point obtained in the work forward direction is:
A posture determining method for an articulated robot, wherein the robot posture is not corrected when the robot posture is substantially the same as the robot posture at the work point obtained in the reverse direction of the work. 4. An apparatus for determining a robot posture at each work point when the articulated robot is moved to a plurality of work points from an original position set in the initial posture and then returned to the original position in the initial posture. A robot posture calculation unit that calculates a robot posture at each work point, a robot movement time calculation unit that calculates a movement time between each work point and each work point from the original position, and A robot posture selection unit that selects, for each work point, a robot posture that minimizes the movement time for each work point; A group selection unit that classifies and selects the group on the downstream side in the work forward direction in which the movement time between the groups is maximum, and the articulated robot A robot posture that corrects the robot posture of the work points that form the downstream side group obtained by moving the robot to the robot posture obtained by moving the articulated robot in the work reverse direction from the original position. A posture determination device for an articulated robot, comprising: a correction unit. 5. The apparatus according to claim 1, further comprising a posture deviation calculation unit that calculates a posture deviation of the end effector of the articulated robot between the work point and each work point from the original position, The posture selection unit, when there are a plurality of robot postures in which the shortest movement time when moving the articulated robot from the original position to each of the work points is substantially the same,
A posture determining apparatus for an articulated robot, characterized in that a robot posture that minimizes the posture deviation is selected.